1. Field of the invention
The present invention relates to an unfoldable divergent nozzle for a rocket engine. More particularly it relates to such an unfoldable divergent nozzle comprising a set of elementary individual panels of refractory material articulated to one another and with respect to a fixed upstream portion of the divergent nozzle in the vicinity of the neck of the nozzle, the articulated panels being distributed so as to define at least two successive adjacent rings of frustums and to be positionable in a first folded position then in a second unfolded position, each panel having an inner surface designed to form a portion of the inner wall of the divergent nozzle, and an outer surface designed to form a portion of the outer wall of the divergent nozzle.
2. Description of the Prior Art
It is known, in the technology of powder rocket motors, to use an unfoldable divergent nozzle, that is to say a divergent nozzle which is held in folded position before firing, in order to assist in the forming of a rocket motor of small size, and then is unfolded after ignition of the rocket motor when the missile is in free flight and is no longer subject to length limitations, in order to contribute to increasing the expansion ratio of the gases in the nozzle, and hence to improve the propulsion efficiency.
The possibility of benefiting from an improved propulsion efficiency, due to the fact of the large size of the unfolded divergent nozzle, without the dimensions of the rocket engine before firing being themselves increased, constitutes an appreciable advantage. However, the practical construction of such unfoldable divergent nozzles is not free of posing a certain number of problems. Thus, according to one technique which can be envisaged, consisting of forming an unfoldable divergent nozzle from a set of articulated panels or petals, it is difficult to form articulations capable of resisting the severe environmental stresses caused by the flow of hot gases in the nozzle, when the divergent nozzle is in unfolded position.
It is an object of the present invention to overcome the aforesaid drawbacks and to provide an unfoldable divergent nozzle of the articulated panel type whose reliability is increased, notably due to the fact of the construction adopted for the various articulations of the panels.